Modulation of Rainfall Patterns and Extreme Events in Ecuador under Multidecadal ENSO Influence

Ecuador’s equatorial location and diverse topography, spanning coastal plains, Andean highlands, and Amazonian rainforests, result in complex rainfall regimes strongly modulated by the El Niño–Southern Oscillation (ENSO). This study investigates the evolution of rainfall climatology and the predictability of extreme precipitation events over two distinct periods (1981–1999 and 2000–2018), focusing on the multidecadal modulation of ENSO’s impacts. Using homogenized daily precipitation data from over 1,000 stations provided by the Instituto Nacional de Meteorología e Hidrología (INAMHI) and satellite-derived datasets (MSWEP, IMERG, CHIRPS), we analyze seasonal rainfall patterns and extreme events through climatic indices such as Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), R95p, R99p, Rx1day, and Rx5days.

Significant shifts in precipitation patterns were observed, with a marked increase in dry spells (CDD) in the coastal region and a reduction in wet days (CWD) and extreme precipitation events (R95p, R99p) in the Andes during 2000–2018 compared to 1981–1999. The teleconnection with ENSO also evolved: while Niño 1+2 dominated rainfall variability in the earlier period, Niño 3.4 and Niño 4 anomalies became more influential post-2000, particularly during the dry season (JAS) and transitional periods (OND). These changes indicate reduced predictability of extreme rainfall events using traditional ENSO indices, highlighting increased hydroclimatic risks, including droughts in the Amazonía and flooding in coastal areas. By integrating in-situ and satellite data, this study enhances the understanding of storm climatologies and provides critical insights for refining seasonal forecasting and climate adaptation strategies. These findings underscore the urgent need to reassess climate risk in Ecuador under a changing climate, offering valuable guidance for mitigating the impacts of extreme weather on agriculture, infrastructure, and ecosystems.